U.S. patent application number 12/170530 was filed with the patent office on 2010-01-14 for zinc containing glasses and enamels.
This patent application is currently assigned to FERRO CORPORATION. Invention is credited to George E. Sakoske.
Application Number | 20100009836 12/170530 |
Document ID | / |
Family ID | 41505681 |
Filed Date | 2010-01-14 |
United States Patent
Application |
20100009836 |
Kind Code |
A1 |
Sakoske; George E. |
January 14, 2010 |
Zinc Containing Glasses And Enamels
Abstract
This invention relates to lead free, cadmium free, bismuth free
low melting high durability glass and enamel compositions. The
compositions comprise silica, zinc, titanium, and boron oxide based
glass frits. The resulting compositions can be used to decorate and
protect automotive, beverage, architectural, pharmaceutical and
other glass substrates.
Inventors: |
Sakoske; George E.;
(Washington, PA) |
Correspondence
Address: |
RANKIN, HILL & CLARK LLP
23755 Lorain Road - Suite 200
North Olmsted
OH
44070-2224
US
|
Assignee: |
FERRO CORPORATION
Cleveland
OH
|
Family ID: |
41505681 |
Appl. No.: |
12/170530 |
Filed: |
July 10, 2008 |
Current U.S.
Class: |
501/14 ;
427/376.2 |
Current CPC
Class: |
C03C 8/18 20130101; C03C
2217/72 20130101; C03C 8/14 20130101; C03C 17/04 20130101; C03C
8/06 20130101 |
Class at
Publication: |
501/14 ;
427/376.2 |
International
Class: |
C03C 8/00 20060101
C03C008/00; B05D 3/02 20060101 B05D003/02 |
Claims
1. An enamel composition comprising, prior to firing: a. 38-60 wt %
SiO.sub.2, b. 5.1-22.9 wt % B.sub.2O.sub.3, c. 8.1-18 wt %
TiO.sub.2, d. 0.1-14.9 wt % ZnO, e. 0.1-4.5 wt % Li.sub.2O f.
0.1-18 wt % K.sub.2O, and g. 1-7 wt % F.
2. The enamel composition of claim 1, further comprising at least
one selected from the group consisting of: a. 0.1-1.9 wt %
Al.sub.2O.sub.3, b. 0.1-4 wt % ZrO.sub.2, and c. 0.1-13 wt %
Na.sub.2O.
3. The enamel composition of claim 1, comprising: a. 41-51 wt %
SiO.sub.2, b. 6-17 wt % B.sub.2O.sub.3, c. 8.5-13 wt % TiO.sub.2,
d. 5.1-13 wt % ZnO, e. 0.1-3 wt % Li.sub.2O f. 1-7.9 wt % K.sub.2O,
and g. 1.5-6 wt % F.
4. The enamel composition of claim 3, further comprising at least
one selected from the group consisting of: a. 0.1-0.95 wt %
Al.sub.2O.sub.3, b. 0.1-1.5 wt % ZrO.sub.2, and c. 5-12 wt %
Na.sub.2O.
5. The enamel composition of claim 1, comprising: a. 45-50 wt %
SiO.sub.2, b. 8 -15 wt % B.sub.2O.sub.3 c. 8.5-11.5 wt % TiO.sub.2,
d. 8-12 wt % ZnO, and e. 0.5-2.5 wt % Li.sub.2O f. 1.7-4 wt %
K.sub.2O, and g. 2-5 wt % F.
6. The enamel composition of claim 5, further comprising at least
one selected from the group consisting of: a. 0.1-0.8 wt %
Al.sub.2O.sub.3, b. 0.1-0.8 wt % ZrO.sub.2, and c. 8-11 wt %
Na.sub.2O.
7. The enamel composition of claim 1 further comprising sulfur,
provided the amount does not exceed about 4 wt %, or a sufficient
amount of a metallic sulfide so as to provide an amount of sulfur
to the enamel composition not exceeding about 4 wt %, prior to
firing.
8. The enamel composition of claim 1, further comprising at least
one of: (a) 0.1-4.9 wt % Bi.sub.2O.sub.3, (b) 0.1-2 wt % Cs.sub.2O,
(c) 0.1-5 wt % MgO, (d) 0.1-5 wt % CeO.sub.2, (e) 0.1-10 wt % MnO,
(f) 0.1-5 wt % CuO, (g) 0.1-5 wt % NiO, (h) 0.1-10 wt % SnO, (i)
0.1-5 wt % P.sub.2O.sub.5, (j) 0.1-10 wt % V.sub.2O.sub.5, (k)
0.1-5 wt % La.sub.2O.sub.3, (l) 0.1-5 wt % Pr.sub.2O.sub.3, (m)
0.1-5 wt % Y.sub.2O.sub.3, (n) 0.1-5 wt % In.sub.2O.sub.3, (o)
0.1-10 wt % Fe.sub.2O.sub.3, (p) 0.1-5 wt % Cr.sub.2O.sub.3, (q)
0.1-5 wt % CoO, (r) 0.1-4 wt % Nb.sub.2O.sub.5, (s) 0.1-4 wt %
WO.sub.3, (t) 0.1-4 wt % MoO.sub.3, and combinations thereof.
9. The enamel composition of claim 1, further comprising at least
one crystalline seed material of a type selected from the group
consisting of zinc borates, zinc silicates, zinc titanates,
aluminum silicates, and combinations thereof.
10. The enamel composition of claim 1, wherein the composition
lacks intentionally added bismuth in any form.
11. A method of decorating a substrate comprising: a. applying to a
enamel substrate a coating of an enamel composition comprising,
prior to firing: i. 38-60 wt % SiO.sub.2, ii. 5.1-22.9 wt %
B.sub.2O.sub.3, iii. 8.1-18 wt % TiO.sub.2, iv. 0.1-14.9 wt % ZnO,
v. 0.1-4.5 wt % Li.sub.2O vi. 0.1-18 wt % K.sub.2O, and vii. 1-7 wt
% F. b. firing the substrate and coating at a temperature
sufficient to flow the enamel composition to cause the enamel
composition to adhere to the substrate.
12. The method of claim 11, wherein, prior to firing, the enamel
composition further comprising at least one selected from the group
consisting of: a. 0.1-1.9 wt % Al.sub.2O.sub.3, b. 0.1-4 wt %
ZrO.sub.2, and c. 0.1-13wt % Na.sub.2O.
13. The method of claim 11, wherein the enamel composition
comprises, prior to firing: a. 41-51 wt % SiO.sub.2, b. 6-17 wt %
B.sub.2O.sub.3, c. 8.5-13 wt % TiO.sub.2, d. 5.1-13 wt % ZnO, e.
0.1-3 wt % Li.sub.2O f. 1-7.9 wt % K.sub.2O, and g. 1.5-6wt %
F.
14. The method of claim 13, wherein the enamel composition further
comprises: a. 0.1-0.95 wt % A.sub.2O.sub.3, b. 0.1-1.5 wt %
ZrO.sub.2, and c. 5-12 wt % Na.sub.2O.
15. The method of claim 13, wherein the enamel composition
comprisies: a. 45-50 wt % SiO.sub.2, b. 8 -15 wt % B.sub.2O.sub.3
c. 8.5-11.5 wt % TiO.sub.2, d. 8-12 wt % ZnO, and e. 0.5-2.5 wt %
Li.sub.2O f. 1.7-4 wt % K.sub.2O, and g. 2-5 wt % F.
16. The method of claim 15, wherein the enamel composition further
comprises: a. 0.1-0.8 wt % Al.sub.2O.sub.3, b. 0.1-0.8 wt %
ZrO.sub.2, and c. 8-11 wt % Na.sub.2O.
17. The method of claim 1 1, wherein the enamel composition further
comprises sulfur, provided the amount does not exceed about 4 wt%,
or a sufficient amount of a metallic sulfide so as to provide an
amount of sulfur to the enamel composition not exceeding about 4 wt
%, prior to firing.
18. The method of claim 11, wherein the enamel composition further
comprises at least one selected from the group consisting of: (a)
0.1-4.9 wt % Bi.sub.2O.sub.3, (b) 0.1-2 wt % Cs.sub.2O, (c) 0.1-5
wt % MgO, (d) 0.1-5 wt % CeO.sub.2, (e) 0.1-10 wt % MnO, (f) 0.1-5
wt % CuO, (g) 0.1-5 wt % NiO, (h) 0.1-10 wt % SnO, (i) 0.1-5 wt %
P.sub.2O.sub.5, (j) 0.1-10 wt % V.sub.2O.sub.5, (k) 0.1-5 wt %
La.sub.2O.sub.3, (l) 0.1-5 wt % Pr.sub.2O.sub.3, (m) 0.1-5 wt %
Y.sub.2O.sub.3, (n) 0.1-5 wt % In.sub.2O.sub.3, (o) 0.1-10 wt %
Fe.sub.2O.sub.3, (p) 0.1-5 wt % Cr.sub.2O.sub.3, (q) 0.1-5 wt %
CoO, (r) 0.1-4 wt % Nb.sub.2O.sub.5, (s) 0.1-4 wt % WO.sub.3, (t)
0.1-4 wt % MoO.sub.3, and combinations thereof.
19. An automotive enamel bearing a fired coating, the fired coating
comprising, prior to firing, a. 38-60 wt % SiO.sub.2, b. 5.1-22.9
wt % B.sub.2O.sub.3, c. 8.1-18 wt % TiO.sub.2, d. 0.1-14.9 wt %
ZnO, e. 0.1-4.5 wt % Li.sub.2O f. 0.1-18 wt % K.sub.2O, and g. 1-7
wt % F.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] This invention relates to low-firing, high durability glass
and enamel compositions. In particular, the invention relates to
glass frit compositions, and the glasses, ceramics and enamels made
therefrom, which include ZnO, SiO.sub.2, B.sub.2O.sub.3 and
TiO.sub.2. The glasses have good acid resistance, low CTE
(<100.times.10.sup.-7) and relatively low firing temperatures
(<1100.degree. F.). All of this is achieved without the use of
lead or bismuth.
[0003] 2. Description of Related Art
[0004] Glass enamel compositions are well known in the art. One aim
of conventional glass and enamel compositions is the achievement of
a low firing, high durability glass and enamel having a low
coefficient of thermal expansion (CTE). However, such glasses
typically require the use of substantial amounts of relatively
expensive Bi.sub.2O.sub.3.
[0005] Partially crystallizing glass enamel compositions that fuse
at relatively low temperatures are used, for example, to form
opaque dark-colored enamel bands on the outer edges of sections of
automotive glass such as windshields and side and rear windows.
These opaque dark-colored enamel bands, which typically vary in
width from about 1.5 cm to about 15.0 cm, greatly enhance the
aesthetic appearance of the sections of glass upon which they are
applied and also block the transmission of sunlight through the
glass to protect underlying adhesives from degradation by
ultraviolet radiation. Moreover, these opaque colored enamel bands
preferably have the ability to conceal silver-containing buss bars
and wiring connections of rear glass defrosting systems from view
from the outside of the vehicle.
[0006] Specially formulated glass enamel compositions can be
applied to planar sections of glass and fired to form opaque
dark-colored enamel bands at the same time as the bending or
forming operations were performed on the section of glass. Such
glass enamel compositions can fuse and partially crystallize at the
temperature at which a section of glass would be preheated
preparatory to a bending or forming operation. It is believed that
the partial crystallization of the enamel forms a dense, hard,
protective layer that prevents the enamel from sticking to the
press or vacuum head during the glass bending and transporting
operations.
[0007] An example of a high durability glass and enamel
compositions is a partially crystallizing lead-free and
cadmium-free glass and enamel compositions including substantial
amounts of SiO.sub.2, TiO.sub.2, Bi.sub.2O.sub.3, and ZnO. U.S.
Pat. No. 6,936,556 to Sridharan is representative of this type. The
partially crystallizing glass and enamel compositions form residual
glass and non-silicate crystals upon firing. A predominant portion
of the non-silicate crystals are titanate crystals, typically
bismuth titanate or zinc titanate.
[0008] Although improvements have been made in recent years, the
chemical durability of known lead-free and cadmium-free glass
enamel systems used in tableware, decorative ware, and automotive
glass applications has been less than desired. Further, the
presence of bismuth, an increasingly expensive metal, has been
required in such formulations as a lead replacement. Therefore, a
need exists for lead-free and cadmium-free (and preferably
bismuth-free) enamel compositions that exhibit excellent chemical
durability to acids, water, and alkalis. Such enamel compositions
must be able to fuse and preferably, partially crystallize at
temperatures at which sections of glass are preheated preparatory
to forming operations so as not to stick to press or vacuum heads.
Moreover, such enamel compositions should be effective in blocking
ultraviolet radiation and in retarding the migration of silver and
subsequent showing from overprinted buss bars and wiring
corrections of rear glass defrosting systems.
BRIEF SUMMARY OF THE INVENTION
[0009] The invention relates to a range of low firing, high
durability glasses, glass frits, and glass enamel compositions.
Automotive designs employ a black glass-ceramic enamel obscuration
band around the periphery of glass windshields to hide unevenness
and protect the underlying adhesive from ultraviolet degradation.
Architectural, appliance, and container/dishware glass applications
often include glass ceramic materials for decorative purposes.
Conventional low firing, high durability enamel systems require the
use of expensive bismuth borosilicate glass frits. The invention
relates to a range of glass frits including the oxides of zinc,
boron, titanium and silicon. The glass and enamel compositions
fired therefrom will pass high durability acid testing, including,
for example, performance of more than six hours in 0.1 N
H.sub.2SO.sub.4 at 80.degree. C. In addition, crystalline seed
materials including, for example zinc borates, zinc titanates,
aluminum silicates and others are compatible with the enamel
composition herein, and can yield anti-stick properties
advantageous in press-bend forming operations such as those used in
the automotive glass industry.
[0010] In particular, the invention provides a glass and enamel
compositions comprising, prior to firing: (a) 38-60 wt % SiO.sub.2,
(b) 5.1-22.9 wt % B.sub.2O.sub.3, (c) 8.1-18 wt % TiO.sub.2, (d)
0.1-14.9 wt % ZnO, (e) 0.1-4.5 wt % Li.sub.2O (f) 0.1-18 wt %
K.sub.2O, and (g) 1-7 wt % F.
[0011] In another embodiment, the invention involves a method of
decorating a substrate comprising (a) applying to a glass substrate
a coating of an enamel composition comprising, prior to firing: (i)
38-60 wt % SiO.sub.2, (ii) 5.1-22.9 wt % B.sub.2O.sub.3, (iii)
8.1-18 wt % TiO.sub.2, (iv) 0.1-14.9 wt % ZnO, (v) 0.1-3.5 wt %
Li.sub.2O (vi) 0.1-18 wt % K.sub.2O, and (vii)1-7 wt % F, and (b)
firing the substrate and coating at a temperature sufficient to
flow the enamel composition to cause the enamel composition to
adhere to the substrate.
[0012] Finally, the invention includes an automotive glass bearing
a fired coating, the fired coating comprising, prior to firing, (a)
38-60 wt % SiO.sub.2, (b) 5.1-22.9 wt % B.sub.2O.sub.3, (c) 8.1-18
wt % TiO.sub.2, (d) 0.1-14.9 wt % ZnO, (e) 0.1-4.5 wt % Li.sub.2O
(f) 0.1-18 wt % K.sub.2O, and (g) 1-7 wt % F.
[0013] The foregoing and other features of the invention are
hereinafter more fully described and particularly pointed out in
the claims, the following description setting forth in detail
certain illustrative embodiments of the invention, these being
indicative, however, of but a few of the various ways in which the
principles of the present invention may be employed.
DETAILED DESCRIPTION OF THE INVENTION
[0014] A glass and enamel compositions of the invention comprises a
combination of the oxides of zinc, boron, silicon and titanium, as
well as fluoride ion.
[0015] In particular, the invention provides a glass and enamel
compositions comprising, prior to firing: (a) 38-60 wt % SiO.sub.2,
(b) 5.1-22.9 wt % B.sub.2O.sub.3, (c) 8.1-18 wt % TiO.sub.2, (d)
0.1-14.9 wt % ZnO, (e) 0.1-4.5 wt % Li.sub.2O (f) 0.1-18 wt %
K.sub.2O, and (g) 1-7 wt % F.
[0016] In another embodiment, the invention involves a method of
decorating a substrate comprising (a) applying to a glass substrate
a coating of an enamel composition comprising, prior to firing: (i)
38-60 wt % SiO.sub.2, (ii) 5.1-22.9 wt % B.sub.2O.sub.3, (iii)
8.1-18 wt % TiO.sub.2, (iv) 0.1-14.9 wt % ZnO, (v) 0.1-4.5 wt %
Li.sub.2O (vi) 0.1-18 wt % K.sub.2O, and (vii)1-7 wt % F, and (b)
firing the substrate and coating at a temperature sufficient to
flow the enamel composition to cause the enamel composition to
adhere to the substrate.
[0017] Finally, the invention includes an automotive glass bearing
a fired coating, the fired coating comprising, prior to firing, (a)
38-60 wt % SiO.sub.2, (b) 5.1-22.9 wt % B.sub.2O.sub.3, (c) 8.1-18
wt % TiO.sub.2, (d) 0.1-14.9 wt % ZnO, (e) 0.1-4.5 wt % Li.sub.2O
(f) 0.1-18 wt % K.sub.2O, and (g) 1-7 wt % F.
[0018] The components of the inventive compositions, articles and
methods are detailed hereinbelow. Compositional percentages are by
weight. All percentages, temperatures, times, and ranges of other
values are presumed to be accompanied by the modifier "about."
[0019] All compositional percentages are by weight and are given
for a blend prior to firing. Details on each ingredient follow.
[0020] Glass Component. The principal glass and enamel compositions
herein include SiO.sub.2, B.sub.2O.sub.3, TiO.sub.2, ZnO,
Li.sub.2O, K.sub.2O and F.sub.2. In particular, broad and preferred
embodiments of the glass and enamel compositions herein are
detailed below. The glass frit compositions herein include
SiO.sub.2: broadly 38-60%, preferably 41-51% and more preferably
45-50%; B.sub.2O.sub.3: broadly 5.1-22.9%; preferably 6-17% and
more preferably 8-15%; TiO.sub.2: broadly 8.1-18 wt %, preferably
8.5-13% and more preferably 11-15%; ZnO: broadly 0.1-14.9%;
preferably 5.1-13%; more preferably 8-12%; Li.sub.2O: broadly
0.1-4.5%, preferably 0.1-3%, more preferably 0.5-2.5%; K.sub.2O:
broadly 0.1-18%; preferably 1-7.9%, more preferably 1.7-4%; and F:
broadly 1-7%, preferably 1.5-6%, more preferably 2-5%.
[0021] Other embodiments are possible, using, for example, a
combination of ranges of oxides indicated as "broad," "preferred"
and "more preferred" in various combinations, so long as such
combination can add up to 100 wt %. For example, 38-60 wt %
SiO.sub.2; 8-15 wt % B.sub.2O.sub.3; 8.5-13 wt % TiO.sub.2 8-12 wt
% ZnO, 0.1-4.5 wt % Li.sub.2O, 0.1-18 wt % K.sub.2O, and 1-7 wt %
F. Another possible embodiment is 41-51 wt % SiO.sub.2, 5.1-22.9 wt
% B.sub.2O.sub.3, 11-15 wt % TiO.sub.2, 5.1-13 wt % ZnO, 0.1-3 wt %
Li.sub.2O, 1-7.9 wt % K.sub.2O and 1-7 wt % F. Other combinations
are possible.
[0022] Secondary, optional oxides may be added to frits according
to the formulations in the preceding two paragraphs in the
following weight percentages: Al.sub.2O.sub.3, 0.1-1.9%, preferably
0.1-0.95, more preferably 0.1-0.8%; ZrO.sub.2: 0.1-4%, preferably
0.1-1.5%, more preferably 0.1-0.8%; and Na.sub.2O: 0.1-13%,
preferably 5-12%, more preferably 8-11%.
[0023] Additional oxides can be added to any previously described
embodiment, singly, or in any combination, up to the noted weight
percentage: Cs.sub.2O 2%; MgO: 5%; CeO.sub.2: 5%; MnO: 10%; CuO:
5%; NiO 5%; SnO: 10%; P.sub.2O.sub.5: 5%; V.sub.2O.sub.5: 10%;
La.sub.2O.sub.3: 5%; Pr.sub.2O.sub.3: 5%; In.sub.2O.sub.3: 5%;
Fe.sub.2O.sub.3: 10%; Cr.sub.2O.sub.3: 5%; CoO: 5%;
Nb.sub.2O.sub.5: 4; WO.sub.3: 4; MoO.sub.3: 4. In a preferred
embodiment, the glass and enamel compositions herein further
comprise at least one of the noted additional oxides where the
range has a lower bound of 0.1%. The glass and enamel compositions
herein may also include 0.1-4.9% Bi.sub.2O.sub.3, but this is not
preferred.
[0024] As can be seen above, the composition of the glass frits
useful in this invention can be adapted over a broad range of oxide
compositions. Glasses may be formulated according to the principal
glass and enamel compositions above, together with, optionally one
or more secondary or additional oxides. The glass and enamel
compositions herein typically contain low amounts of PbO, CdO and
Bi.sub.2O.sub.3, i.e., less than 5 wt % of each, preferably less
than 1 wt % of each, more preferably less than 0.5 wt % of each,
and even more preferably, less than 0.1 wt % of each. Most
preferably, the glass and enamel compositions herein are devoid of
intentionally added PbO, CdO, and Bi.sub.2O.sub.3. However, certain
embodiments not involving food or beverage storage may
intentionally include oxides of lead or oxides of cadmium or oxides
of bismuth, or any combination thereof.
[0025] Sulfide glass frits are glass frits that contain a metal
sulfide component. Certain embodiments of the invention include
sulfide ions provided by elemental sulfur or metallic sulfides.
Exemplary sulfide glass frits are disclosed in U.S. Pat. No.
5,350,718 to Antequil et al., which is hereby incorporated by
reference. Exemplary sulfides in such frits include ZnS, MnS, FeS,
CoS, NiS, Cu.sub.2S, CdS, Sb.sub.2S.sub.3 and Bi.sub.2S.sub.3. In
particular, the glass and enamel compositions herein may include
0-4 wt % sulfur, or a sufficient amount of a metallic sulfide so as
to provide 0-4 wt % sulfur to a glass and enamel compositions,
prior to firing.
[0026] A glass component containing both oxide and sulfide frits
are also envisioned. The glass frits useful herein have melting
points in the range of about 1000.degree. F. to 1400.degree. F., or
any intermediate temperature such as 1030.degree. F., 1040.degree.
F., 1050.degree. F., 1060.degree. F., 1080.degree. F., 1110.degree.
F., 1150.degree. F., 1190.degree. F., 1200.degree. F., 1210.degree.
F., 1250.degree. F., 1275.degree. F., 1300.degree. F., various of
the frits may be effectively fired at those temperatures.
Preferably, the glass frits herein can be fired at
1000-1250.degree. F., more preferably at 1020-1200.degree. F.,
still more preferably at about 1030-1150.degree. F., and most
preferably at about 1040-1100.degree. F.
[0027] Generally, the glass frits are formed in a known manner, for
example, blending the starting materials (oxides and/or sulfides)
and melting together at a temperature of about 1000 to about
1400.degree. C. (about 1830 to about 2550.degree. F.) for about 45
to about 75 minutes to form a molten glass having the desired
composition. The molten glass formed can then be suddenly cooled in
a known manner (e.g., water quenched) to form a frit. The frit can
then be ground using conventional milling techniques to a fine
particle size, from about 1 to about 8 microns, preferably 2 to
about 6 microns, and more preferably about 3 to about 5
microns.
[0028] Crystalline Material. Crystalline materials may be included
along with the frit compositions herein to promote crystallization.
Crystalline materials useful herein include zinc silicates, zinc
borates, zinc titanates, silicon zirconates, aluminum silicates,
calcium silicates, and combinations thereof. The crystalline
materials may include, without limitation, Zn.sub.2SiO.sub.4,
2ZnO.3TiO.sub.2, ZnTiO.sub.3, ZnO.B.sub.2O.sub.3,
3ZnO.B.sub.2O.sub.3, 5ZnO.2B.sub.2O.sub.3, and Al.sub.2SiO.sub.5.
The Ruderer U.S. Pat. No. 5,153,150 and Sakoske U.S. Pat. No.
5,714,420 patents noted hereinabove provide further information on
crystalline materials. Preferred crystalline materials include zinc
silicates such as Zn.sub.2SiO.sub.4 and zinc borosilicates such as
ZnO.B.sub.2O.sub.3. Specific examples of seed materials used herein
include product numbers 2077 (bismuth silicate seed material) and
2099 (zinc silicate seed material) manufactured by Ferro Glass and
Color Corporation.
[0029] Organic Vehicle. When applied by procedures requiring one,
such as screen printing, the foregoing solid ingredients may be
combined with an organic vehicle to form a green glass enamel
composition, which is a paste. The green paste in general contains
60 to 90% solids as above described and 10 to 40% of an organic
vehicle. The viscosity of the paste is adjusted so that it can be
screen-printed, roll coated, sprayed, or otherwise applied in a
desired manner onto the desired substrate.
[0030] The organic vehicle comprises a binder and a solvent, which
are selected based on the intended application. It is essential
that the vehicle adequately suspend the particulates (i.e., frit,
crystalline material) and burn off completely upon firing. In
particular, binders including methyl cellulose, ethyl cellulose,
and hydroxypropyl cellulose, and combinations thereof, may be used.
Suitable solvents include propylene glycol, diethylene glycol butyl
ether; 2,2,4-trimethyl pentanediol monoisobutyrate (Texanol.TM.);
alpha-terpineol; beta-terpineol; gamma terpineol; tridecyl alcohol;
diethylene glycol ethyl ether (Carbitol.TM.), diethylene glycol
butyl ether (Butyl Carbitol.TM.); pine oils, vegetable oils,
mineral oils, low molecular weight petroleum fractions, tridecyl
alcohols, and synthetic or natural resins and blends thereof.
Surfactants and/or other film forming modifiers can also be
included. The solvent and binder may be present in a weight ratio
of about 50:1 to about 20:1. The preferred vehicle is a combination
of Butyl Carbitol.TM. (diethylene glycol monobutyl ether) and ethyl
cellulose in a weight ratio of about 200:1 to 20:1, 50:1 to about
20:1, more preferably about 40:1 to about 25:1.
[0031] In general, the enamel pastes are viscous in nature, with
the viscosity depending upon the application method to be employed
and end use. For purposes of screen-printing, viscosities ranging
from 10,000 to 80,000, preferably 15,000 to 35,000 centipoise, and
more preferably 18,000 to 28,000 centipoise at 20.degree. C., as
determined on a Brookfield Viscometer, #29 spindle at 10 rpm, are
appropriate.
[0032] Pigments. In certain embodiments, the glass frit can be
combined with a mixed metal oxide pigment. When used, such pigments
generally constitute no greater than about 30 wt %, and preferably
no greater than about 25 wt %, of the glass enamel compositions
herein, depending upon the range of color, gloss, and opacity
(i.e., transmittance) desired.
[0033] Keeping in mind the general preference for completely
lead-free, cadmium-free, and bismuth-free compositions for food and
beverages, useful pigments may come from several of the major
classifications of complex inorganic pigments, including
corundum-hematite, olivine, priderite, pyrochlore, rutile, spinel,
and spinel, though other categories such as baddeleyite, borate,
garnet, periclase, phenacite, phosphate, sphene and zircon may be
suitable in certain applications. Oxides of the metals cobalt,
chromium, manganese, praseodymium, iron, nickel, and copper are
often useful. In particular, specific pigments include cobalt
silicate blue olivine Co.sub.2SiO.sub.4; nickel barium titanium
primrose priderite 2NiO:3BaO:17TiO.sub.2; nickel antimony titanium
yellow rutile (Ti,Ni,Nb)O.sub.2; nickel niobium titanium yellow
rutile (Ti,Ni,Nb)O.sub.2; nickel tungsten yellow rutile
(Ti,Ni,W)O.sub.2; chrome antimony titanium buff (Ti,Cr,Sb)O.sub.2;
chrome niobium titanium buff rutile (Ti,Cr,Nb)O.sub.2; chrome
tungsten titanium buff rutile (Ti,Cr,W)O.sub.2; manganese antimony
titanium buff rutile (Ti,Mn,Sb)O.sub.2; titanium vanadium grey
rutile (Ti,V,Sb)O.sub.2; manganese chrome antimony titanium brown
rutile (Ti,Mn,Cr,Sb)O.sub.2; manganese niobium titanium brown
rutile (Ti,Mn,Nb)O.sub.2; cobalt aluminate blue spinel
CoAl.sub.2O.sub.4; zinc chrome cobalt aluminum spinel
(Zn,Co)(Cr,Al).sub.2O.sub.4; cobalt chromate blue-green spinel
CoCr.sub.2O.sub.4; cobalt titanate green spinel Co.sub.2TiO.sub.4;
iron chromite brown spinel Fe(Fe,Cr).sub.2O.sub.4; iron titanium
brown spinel Fe.sub.2TiO.sub.4; nickel ferrite brown spinel
NiFe.sub.2O.sub.4; zinc ferrite brown spinel
(Zn,Fe)Fe.sub.2O.sub.4; zinc iron chromite brown spinel
(Zn,Fe)(Fe,Cr).sub.2O.sub.4; copper chromite black spinel
CuCr.sub.2O.sub.4; iron cobalt chromite black spinel
(Co,Fe)(Fe,Cr).sub.2O.sub.4; chrome iron manganese brown spinel
(Fe,Mn)(Cr,Fe).sub.2O.sub.4; chrome iron nickel black spinel
(Ni,Fe)(Cr,Fe).sub.2O.sub.4; and chrome manganese zinc brown spinel
(Zn,Mn)(Cr.sub.2O.sub.4). Only in applications where lead is
permitted (i.e., other than food or beverage containers, tableware,
etc.), lead antimonite yellow pyrochlore (Pb.sub.2Sb.sub.2O.sub.7)
or other lead-containing pigments may be used. Commercially
available examples of suitable pigments are available from Ferro
Glass and Color Corporation, such as 2991 pigment (copper chromite
black), 2980 pigment (cobalt chromium iron black), 2987 pigment
(nickel manganese iron chromium black), and 0-1776 pigment (black).
Pigments free from Co, Cu, Cr, Ni and the like such a 10201 black
(bismuth manganate) would also be suitable.
[0034] Especially preferred are pigments having the following Ferro
Corporation part numbers and formulas: K393 (CuCrMn),
V792(NiMnCrFe), 2503(CdSeS), 2336(CoAl), and 2501(CdSeS).
[0035] Properties. The glass articles herein are coated in order to
impart desired properties to the article. The properties of acid
resistance, heavy metal release, color, gloss, and light
transmittance, characterize the final finished products are
detailed hereinbelow.
[0036] Acid Resistance. The glass and enamel compositions herein,
and the fired glass, ceramic, and enamel coatings obtained by the
firing thereof are often used in harsh environments, including, for
example, automotive or architectural glass, institutional table
ware, and others.
[0037] Heavy Metal Release. Because the inventive glass and enamel
compositions herein may be used to decorate glassware for
preparing, serving, and storing food, it is important that such
compositions contain extremely low concentrations of toxic heavy
metals, such as lead and cadmium. Further, in the in the inevitable
event that the glass and enamel compositions contains a small
portion of such toxic metals, it is important that the glass and
enamel compositions do not release the heavy metals, or do so only
in minute concentrations. Foe example, it is an advantage of the
glass and enamel compositions herein release less than 100 ppm of
heavy metals of any kind when subjected to a strong detergent
attack as set forth in DTM 77, described hereinbelow. It is more
preferred that the glass and enamel compositions release less than
75 ppm, and even more preferred when less than 50 ppm is released.
It is still more preferred that less than 25 ppm be released.
[0038] Dispersing Surfactant. A dispersing surfactant assists in
pigment wetting, when an insoluble particulate inorganic pigment is
used. A dispersing surfactant typically contains a block copolymer
with pigment affinic groups. For example, surfactants sold under
the Disperbyk.RTM. and Byk.RTM. trademarks by Byk Chemie of Wesel,
Germany, such as Disperbyk 162 and 163, which are solutions of high
molecular weight block copolymers with pigment affinic groups, and
a blend of solvents (xylene, butylacetate and
methoxypropylacetate). Disperbyk 162 has these solvents in a 3/1/1
ratio, while the ratio in Disperbyk 163 is 4/2/5. Disperbyk 140 is
a solution of alkyl-ammonium salt of an acidic polymer in a
methoxypropylacetate solvent.
[0039] Rheological Modifier. A rheological modifier is used to
adjust the viscosity of the green pigment package composition. A
variety of rheological modifiers may be used, including those sold
under the Byk.RTM., Disperplast.RTM., and Viscobyk.RTM. trademarks,
available from Byk Chemie. They include, for example, the BYK 400
series, such as BYK 411 and BYK 420, (modified urea solutions); the
BYK W-900 series, (pigment wetting and dispersing additives); the
Disperplast series, (pigment wetting and dispersing additives for
plastisols and organosols); and the Viscobyk series, (viscosity
depressants for plastisols and organosols).
[0040] Flow aid. A flow aid is an additive used to control the
viscosity and rheology of a pigment composition, which affects the
flow properties of liquid systems in a controlled and predictable
way. Rheology modifiers are generally considered as being either
pseudoplastic or thixotropic in nature. Suitable surfactants herein
include those sold commercially under the Additol.RTM.,
Multiflow.RTM., and Modaflow.RTM. trademarks by UCB Surface
Specialties of Smyrna, Georgia. For example, Additol VXW 6388,
Additol VXW 6360, Additol VXL 4930, Additol XL 425, Additol XW 395,
Modaflow AQ 3000, Modaflow AQ 3025, Modaflow Resin, and Multiflow
Resin.
[0041] Adhesion promoter. Adhesion promoting polymers are used to
improve the compatibility between a polymer and a filler. Suitable
adhesion promoters include those sold by GE Silicones of Wilton,
Connecticut under the Silquest.RTM., CoatOSil.RTM., NXT.RTM.,
XL-Pearl.TM. and Silcat.RTM. trademarks. Examples include the
following product numbers, sold under the Silquest.RTM. trademark:
A1101,A1102,A1126,A1128,A1130,A1230,A1310,A162,A174,A178,A187,
A2120. For example, Silquest A-187 is
(3-glycidoxypropyl)trimethoxysilane, which is an epoxysilane
adhesion promoter. The inventors herein have found that aromatic
epoxies crosslinked with amines or amides produced unacceptable
results. Silanes sold by Degussa AG of Dusseldorf, Germany, under
the Dynasylan.RTM. trademark are also suitable. Most preferred
herein is Silquest A187.
[0042] Stabilizers. Light or UV stabilizers are classified
according to their mode of action: UV blockers--that act by
shielding the polymer from ultraviolet light; or hindered amine
light stabilizers (HALS)--that act by scavenging the radical
intermediates formed in the photo-oxidation process. The
compositions of the invention comprise about 0.1 to about 2 wt % of
a light stabilizer, preferably about 0.5 to about 1.5%, and further
comprise about 0.1 to about 4 wt % of a UV blocker, preferably
about 1 to about 3%.
[0043] Light stabilizers and UV blockers sold under the
Irgafos.RTM., Irganox.RTM., Irgastab.RTM., Uvitex.RTM., and
Tinuvin.RTM. trademarks by from Ciba Specialty Chemicals,
Tarrytown, N.Y., may be used, including product numbers 292 HP,
384-2, 400, 405, 41 IL, 5050, 5055, 5060, 5011, all using the
Tinuvin trademark. Suitable UV blocking agents include Norbloc 7966
(2-(2'hydroxy-5' methacryloxyethylphenyl)-2H-benzotriazole);
Tinuvin 123
(bis-(2,2,6,6-tetramethyl-1-(octyloxy)-4-piperidinyl)ester);
Tinuvin 99 (3-(2H-benzotriazole-2-yl) 5-(1,1-dimethyl
ethyl)-4-hydroxybenzenepropanoic acid, C7-9-branched alkyl esters)
Tinuvin 171 (2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methyl-phenol).
Products sold under the Norbloc.RTM. trademark are available from
Janssen Pharmaceutica of Beerse, Belgium.
[0044] Suitable hindered amine light stabilizers (HALS) are sold by
the Clariant Corporation, Charlotte, N.C., under the Hostavin.RTM.
trademark, including Hostavin 845, Hostavin N20, Hostavin N24,
Hostavin N30, Hostavin N391, Hostavin PR31, Hostavin ARO8, and
Hostavin PR25. HALS are extremely efficient stabilizers against
light-induced degradation of most polymers. They do not absorb UV
radiation, but act to inhibit degradation of the polymer, thus
extending its durability. Significant levels of stabilization are
achieved at relatively low concentrations. The high efficiency and
longevity of HALS are due to a cyclic process wherein the HALS are
regenerated rather than consumed during the stabilization process.
They also protect polymers from thermal degradation and can be used
as thermal stabilizers.
[0045] Examples. The following compositions represent exemplary
embodiments of the invention. They are presented to explain the
invention in more detail, and do not limit the invention. High
durability glass and enamel compositions according to the present
invention are given in Table 1, columns 3-9. Conventional zinc
borosilicate frits are given in columns 1 and 2 for comparative
purposes. The thermal expansion coefficient was determined from
room temperature to 300.degree. C. using an Orton model 1000R
dilatometer. The glass transition temperature is Tg and the
dilatometric softening point is Td. The firing temperature
determination is described hereinabove. The "firing temperature" is
the temperature where the frit particles begin to melt and sinter
together upon heating. The room temperature chemical durabilities
were determined as described hereinabove for 4% Acetic acid, 10%
Citric acid, and 10% hydrochloric acid solutions.
[0046] Heavy Metal (cadmium) release of selected enamels in Table 1
is also presented. Sample automotive windshield enamels were also
made using these compositions as presented in Table 2. The paste
ratio is the weight ratio of solid constituents (glass frits,
pigments, metals) to the organic vehicle. The minimum fire of the
enamel is determined as described below. The acid test using 0.1N
H2S04 at 80.degree. C. results are reported in hours, and the wet
through method was used to determine point of failure as described
below. This test is commonly called the Toyota test. Conventional
zinc-based enamels have not been able to survive more than 4 hours
of exposure to 0.1N H.sub.2SO.sub.4 at 80.degree. C.
TABLE-US-00001 TABLE 1 Frit formulations in wt %, firing
temperatures, data on acid resistance and heavy metal release.
Prior art Prior art ZnBSi ZnBSi Formula frit 1 frit 2 Frit A Frit B
Frit C Frit D Frit E Frit F Frit G Oxide Nb.sub.2O.sub.5 0.00 0.00
0.00 0.00 0.00 0.00 0.00 0.00 0.00 CeO.sub.2 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 0.00 SiO.sub.2 20.52 20.31 38.82 43.99 43.50
41.15 38.94 44.24 40.03 TiO.sub.2 0.00 1.64 7.65 9.30 9.19 8.70
12.13 9.35 12.47 ZrO.sub.2 1.15 7.93 0.00 0.66 0.65 0.62 0.58 0.66
0.60 Al.sub.2O.sub.3 3.26 1.64 0.00 0.65 0.64 0.60 0.57 0.65 0.59
B.sub.2O.sub.3 30.09 27.17 9.69 14.06 13.90 13.16 12.45 14.14 12.80
Bi.sub.2O.sub.3 0.00 0.00 0.00 0.00 0.00 0.00 1.48 0.00 0.00
S03*.37 0.00 0.00 0.00 0.00 1.12 1.12 1.06 0.00 0.00 CaO 0.00 5.39
0.00 0.00 0.00 0.00 0.00 0.00 0.00 PbO 0.00 0.00 0.00 0.00 0.00
0.00 0.00 0.00 0.00 ZnO 33.37 24.63 34.38 10.86 10.74 10.36 9.81
10.93 9.89 K.sub.2O 0.00 0.00 6.06 2.30 2.28 17.19 16.27 0.65 16.73
Li.sub.2O 0.00 0.00 1.61 1.91 1.88 1.78 1.69 1.92 1.73 Na.sub.2O
11.61 10.26 1.80 10.58 10.46 0.00 0.00 11.73 0.00 F.sub.2 0.00 1.02
0.00 5.69 5.63 5.32 5.03 5.72 5.17 TEC .times. 10.sup.-7 in/in 75.0
80.0 69.0 87.3 91.0 81.0 86.0 85.9 93.0 .degree. C. Tg .degree. C.
476 -- 485 425 436 480 458 423 440 Td .degree. C. 520 -- 534 475
495 530 515 491 496 Fire Temp 1050 1110 1110 1040 1050 1100 1060
1035 1030 .degree. F. 4% Acetic 4.5 -- 1 2 3 1 1 2 1 10% Citric 6 5
1 4 3 1 2 4 4 10% HCl -- -- 4 4 1 1 1 4 4 HMR [Cd] removed 74.0
200.0 3.1 -- -- -- 3.7 3.0 PPM
TABLE-US-00002 TABLE 2 Enamel formulations in wt %, firing data,
and acid resistance performance data for pastes made with selected
frits from table 1. Prior Art Prior Art Glass Used Enamel 1 Enamel
2 Enamel A Enamel B Enamel C Enamel D Enamel E Prior Art 1 75.00
Prior Art 1 75.00 Glass A 75.00 Glass B 75.00 Glass C 73.70 Glass D
74.70 Glass E 74.70 2099 3.40 3.40 3.40 3.40 5.00 3.00 3.00 2077
1.00 1.00 K393 20.00 20.00 20.00 20.00 O-1776B 19.00 19.00 19.00
V792 2.30 2.30 2.30 Si Metal 1.60 1.60 1.60 1.60 100.0 100.0 100.0
100.0 100.0 100.0 100.0 MIN FIRE .degree. F. 1100 1110 1170 1120
1150 1180 1130 Paste Ratio 4.4 4.2 3.75 4.0 3.7 3.7 3.7 4% Acetic
acid 6 5 3 2 1 1 1 10% Citric acid 7 7 4 3 2 1 1 10% HCl acid 6 6 4
3 3 1 3 0.1 N H.sub.2SO.sub.4 - 80.degree. C. <1 <1 1-2 34-37
50-58 45-49 41-45 (hours)
[0047] The testing procedures used herein are as follows. Firing
Temperature Estimate DTM 59: A screen printable paste is made by
blending 4 g.+-.0.1 grams of test frit with pine oil. After a
ten-minute pre-heat at 800.degree. F., the trials are then rapidly
transferred to a second furnace at a temperature below the expected
firing temperature for the frit for 15 minutes. After 15 minutes in
the second furnace, the trials are removed and cooled. This cycle
is repeated (at higher temperatures) until the printed frit
particles become sintered together and cannot be scratched away.
Once the "firing temperature" has been determined, an underfire of
10.degree. F. below the "firing temperature" is made for
confirmation.
[0048] Acid Test Resistance to 10% Citric Acid at Room Temperature,
ASTM C-724-91. A visual assessment of the resistance of a glass
enamel or frit coating to 10% citric acid at room temperature is
made of any residual stain after exposure to the acid solution. The
same test is conducted with respect to a 4 wt % solution of acetic
acid at room temperature for a one-minute exposure, and a 10 wt %
solution of hydrochloric acid at room temperature for a ten-minute
exposure.
[0049] Heavy Metal Release. Standard test samples are formulated,
fired, and aged. The trials are placed in a 4000 cc stainless steel
beaker containing a solution consisting of: 2000 cc distilled water
and 6 grams of Super Soilax.RTM. detergent. During the detergent
"aging" exposure prior to HMR testing, the entire trial must be
submersed in the solution. The beaker with fired trials is then
placed in a constant temperature water bath at 95.degree. C. for 24
hours. After the trials have been exposed to the heated solution
for 24 hours, the beaker is removed from the water bath, and the
trials are removed from the beaker. The trials are immediately
rinsed with tap water, while rubbing the exposed enamel surface to
remove any residue. The lead and cadmium release values are
obtained by atomic absorption spectrophotometer, and reported as
PPM.
[0050] Additional advantages and modifications will readily occur
to those skilled in the art. Therefore, the invention in its
broader aspects is not limited to the specific details and
illustrative example shown and described herein. Accordingly,
various modifications may be made without departing from the spirit
or scope of the general invention concept as defined by the
appended claims and their equivalents.
* * * * *